Topic

OSI Reference Model

2

3

OSI Reference ModelSimple Video Example

4

5

Topic

TCP/IP Model

7

8

Error Handling

51

Addressing

Connection Establishment

2

Connection Release

3

Flow Control

4

Interface and State Machine

6

Agenda of TCP/IP Model

9

In TCP/IP there are two main transport protocols.

Transport Protocol

TCP UDP

Reliable: if some data is lost somewhere, TCP retransmits it

Stream service: the data is delivered at destination in the order it was sent

by source (sequence guarantee)

Unit of information is a byte; grouping of data into blocks may be different

at destination than at source

In TCP (Transmission Control Protocol)

In UDP (User Datagram Protocol)

offers a datagram service to the application (unit of information is a message)

Unreliable (message may be lost)

No sequence guarantee

10

Topic

LAN & WAN

share peripherals devices like printers

LAN (Local Area Network)

small geographic area

Super cheap

high-speed data network

shared access to devices

And so on ...Everything!

12

•Special security measures are needed to stop the users from using programs and data that they should not have accessed to.•Network are difficult to set up and need to be maintained by skilled technicians.•If the file servers develop a serious fault, all the users are affected, rather than just one users in the case of a standalone machine. •It needs to be on all the time.

Workstations can share peripherals devices like printers. Cheaper that providing a printer for each computer.Workstations do not necessary need their own hard disk or CD-ROM drives which make them cheaper to buy than stand-alone PC.User can save their work centrally on the network’s file server. This means that they can retrieve work from any workstation on the network.They don’t need to go to the same workstation again.

Advantages Disadvantages

LAN

13

network protocols like ATM, X.25, and Frame Relay

WAN (Wide Area Network)

router connects LANs to WANs

broad geographic area

high-speed data network

shared access to devices

And so on ...Everything!

14

WAN (Wide Area Network)

LAN (Local Area Network)

15

16

Topic

Network Topologies

?

What is Network Topology?

• The physical topology of a network refers to the configuration of cables, computers, and other peripherals. Physical topology should not be confused with logical topology which is the method used to pass information between workstations. Logical topology was discussed in the Protocol chapter.

• There are several basic network topologies: star, bus, ring, mesh, and hierarchical etc.. 18

A Star topology• A star network has a central node that

connects to each of the other nodes by a single, point-to-point link. Any communication between one node and another in a star topology must pass through the central node.

19

Bus Topology• In a bus topology, nodes are arranged along a single

length of twisted-pairwire, coaxial cable, or fiber-optic cable that can be extended at the ends. Using a bus topology, it is easy and inexpensive to add a node to the network, and losing a node in the network will not cause the network to fail. The main disadvantages to the bus topology are that a defective bus causes the entire network to fail. Also, providing a bus with inadequate bandwidth will degrade the performance of the network.

20

•There is a limit on central cable length and number of nodes that can be connected.•Dependency on central cable in this topology has its disadvantages.If the main cable (i.e. bus ) encounters some problem, whole network breaks down. •Proper termination is required to dump signals. Use of terminators is must.•It is difficult to detect and troubleshoot fault at individual station.•It is not suitable for networks with heavy traffic.

It is easy to set-up and extend bus network.Cable length required for this topology is the least compared to other networks.Bus topology costs very less.Linear Bus network is mostly used in small networks. Good for LAN.

Advantages Disadvantages

Bus Topology

21

Ring Topology• A network topology that is set up in a circular fashion in which

data travels around the ring in one direction and each device on the right acts as a repeater to keep the signal strong as it travels. Each device incorporates a receiver for the incoming signal and a transmitter to send the data on to the next device in the ring. The network is dependent on the ability of the signal to travel around the ring.

22

A mesh Topology • A mesh network design is one in which each

device is connected to every other device located on the network, like a spider web. The advantage to this design is the redundancy of the connected devices; if one link fails, it will not affect the rest of the network. The disadvantages of this design are the cost of all the required medium and limited scalability. If you add a device to a network that currently has four devices, then you must connect the new device to the four existing devices with individual cable drops.

23

Hierarchical Topology• In a hierarchical topology, nodes are arranged

like an inverted tree with the root (usually the mainframe computer) as the highest level and the leaves (usually the desktop computers) as the lowest level. It is very cheap, but may have possible traffic jams at the top level.

24

Hybrid Topology• In a hybrid topology, nodes are arranged in more

than one topology, which may include star, ring, and hierarchical . A hybrid topology can integrate together various computer configurations that may have special reasons for their own choice of topology. A hybrid network will allow companies to pick the advantages from several different topologies.

25

Topic

Network Technologies

27

•Under heavy use there can be a delay•Data packets can get lost or become corrupted•Protocols are needed for a reliable transfer•Not so good for some types data streams (e.g. real-time video streams can lose frames due to the way packets arrive out of sequence)

SecurityBandwidth used to full potentialDevices of different speeds can communicateNot affected by line failure (redirects signal)Availability – no waiting for a direct connection to become availableDuring a crisis or disaster, when the public telephone network might stop working, e-mails and texts can still be sent via packet switching

Advantages Disadvantages

Packet Switching

28

29

•Inefficient – the equipment may be unused for a lot of the call; if no data is being sent, the dedicated line still remains open.•It takes a relatively long time to set up the circuit.•During a crisis or disaster, the network may become unstable or unavailable.•It was primarily developed for voice traffic rather than data traffic.

Circuit is dedicated to the call – no interference, no sharingGuaranteed the full bandwidth for the duration of the callGuaranteed quality of service

Advantages Disadvantages

Circuit Switching

30

?

What is Frame Relay?Frame Relay is a packet switching technology for connecting network points in Wide Area Networks (WAN). It

is a connection oriented data service and establishes a virtual circuit between two end points. Data transfer is done in packets of data known as frames. These frames are variable in packet size and more efficient due to flexible transfers. Frame Relay was originally introduced for ISDN interfaces though it is currently used over a variety of other network interfaces as well.

In Frame Relay, connections are called as ‘Ports’. All the points which need to connect to the frame relay network needs to have a port. Every port has a unique Address. A frame is made of two parts which can be called as ‘actual data’ and the ‘frame relay header’. Frame architecture is same as defined for LAP-D (Link Access Procedures on the D channel) which has a variable length for information field. These frames are sent over Virtual Connections.

Frame Relay can create multiple redundant connections among various routers, without having multiple physical links. Since frame relay is not specific for media, and provides means to buffer speed variations, it has the possibility to create a good interconnect medium between different types of network points with different speeds. 31

?

What is ATM?ATM is a network switching technology that uses a cell based methodology to quantize data. ATM data

communication consists of fixed size cells of 53 bytes. An ATM cell contains a 5 byte header and 48 bytes of ATM payload. This smaller size, fixed-length cells are good for transmitting voice, image and video data as the delay is minimized.

ATM is a connection oriented protocol and therefore a virtual circuit should be established between sending and receiving points. It establishes a fixed route between two points when the data transfer starts.

ATM is designed to be convenient for hardware implementation and therefore processing and switching have become faster. Bit rates on ATM networks can go up to 10 Gbps. ATM is a core protocol used over the SONET/SDH backbone of the ISDN.

ATM provides a good quality of service in networks where different types of information such as data, voice, and are supported. With ATM, each of these information types can pass through a single network connection.

32

Topic

Transmission Medium

There are two main types of transmission medium

Transmission Medium

Guided (Wired)

Unguided (Wireless)

Bandwidth

higher bandwidth gives higher data rate

Transmission impairments

e.g.. attenuation

Interference

Number of receivers in guided media

more receivers introduces more attenuation

Design Factors

34

Transmission Characteristics of Guided Media

Frequency Range

Frequency Range

Typical Attenuation

Typical Attenuation

Typical DelayTypical Delay Repeater Spacing

Repeater Spacing

Twisted pair (with loading)Twisted pair (with loading)

0 to 3.5 kHz0 to 3.5 kHz 0.2 dB/km @ 1 kHz0.2 dB/km @ 1 kHz

50 µs/km50 µs/km 2 km2 km

Twisted pairs (multi-pair cables)

Twisted pairs (multi-pair cables)

0 to 1 MHz0 to 1 MHz 0.7 dB/km @ 1 kHz0.7 dB/km @ 1 kHz

5 µs/km5 µs/km 2 km2 km

Coaxial cableCoaxial cable 0 to 500 MHz0 to 500 MHz 7 dB/km @ 10 MHz7 dB/km @ 10 MHz

4 µs/km4 µs/km 1 to 9 km1 to 9 km

Optical fiberOptical fiber 186 to 370 THz186 to 370 THz 0.2 to 0.5 dB/km0.2 to 0.5 dB/km

5 µs/km5 µs/km 40 km40 km

35

Twisted Pair

• analog – needs amplifiers every 5km to 6km

• digital– can use either analog or digital signals– needs a repeater every 2-3km

• limited distance• limited bandwidth (1MHz)• limited data rate (100MHz)• susceptible to interference and noise 36

Coaxial Cable

• superior frequency characteristics to TP• performance limited by attenuation & noise• analog signals

– amplifiers every few km– closer if higher frequency– up to 500MHz

• digital signals– repeater every 1km– closer for higher data rates 37

Optical Fiber

• greater capacity– data rates of hundreds of Gbps

• smaller size & weight• lower attenuation• electromagnetic isolation• greater repeater spacing

– 10s of km at least 38

network protocols like ATM, X.25, and Frame Relay

WAN (Wide Area Network)

router connects LANs to WANs

broad geographic area

high-speed data network

shared access to devices

And so on ...Everything!

39

Wireless Transmission

Frequecies

2GHz to 40GHz

30MHz to 1GHz

3 x 1011 to 2 x 1014

microwavehighly directionalpoint to pointsatellite

omnidirectionalbroadcast radio

Infraredlocal

40

Antennas

• electrical conductor used to radiate or collect electromagnetic energy

• transmission antenna– radio frequency energy from transmitter– converted to electromagnetic energy byy antenna– radiated into surrounding environment

• reception antenna– electromagnetic energy impinging on antenna– converted to radio frequency electrical energy– fed to receiver

• same antenna is often used for both purposes41

Radiation Pattern

• power radiated in all directions• not same performance in all directions– as seen in a radiation pattern diagram

• an isotropic antenna is a (theoretical) point in space– radiates in all directions equally– with a spherical radiation pattern

42

Terrestrial Microwave

• used for long haul telecommunications• and short point-to-point links• requires fewer repeaters but line of sight• use a parabolic dish to focus a narrow beam onto a

receiver antenna• 1-40GHz frequencies• higher frequencies give higher data rates• main source of loss is attenuation– distance, rainfall

• also interference43

Satellite Microwave• satellite is relay station• receives on one frequency, amplifies or repeats

signal and transmits on another frequency– eg. uplink 5.925-6.425 GHz & downlink 3.7-4.2 GHz

• typically requires geo-stationary orbit– height of 35,784km– spaced at least 3-4° apart

• typical uses– television– long distance telephone– private business networks– global positioning

44

Satellite Point to Point Link

45

Satellite Broadcast Link

46

Broadcast Radio

• radio is 3kHz to 300GHz• use broadcast radio, 30MHz - 1GHz, for:– FM radio– UHF and VHF television

• is omnidirectional• still need line of sight• suffers from multipath interference– reflections from land, water, other objects

47

Infrared

• modulate noncoherent infrared light• end line of sight (or reflection)• are blocked by walls• no licenses required• typical uses– TV remote control– IRD port

48

Wireless PropagationGround Wave

49

Wireless PropagationSky Wave

50

Wireless PropagationLine of Sight

51

Topic

Communication

Connections between devices may be classified into three categories

Simplex. This is a unidirectional connection, i.e., data can only travel in onedirection. Simplex connections are useful in situations where a device onlyreceives or only sends data (e.g., a printer).

Half-duplex. This is a bidirectional connection, with the restriction that data cantravel in one direction at a time.

Full-duplex. This is a bidirectional connection in which data can travel in bothdirections at once. A full-duplex connection is equivalent to two simplexconnections in opposite directions.

Topic

Network Units

55

Topic

Switching Technologies

•Switch will save the entire packet to the buffer and check it for errors or other problems before sending.•If the packet has an error, it is discarded.•Entire packet is processed•Packets are filtered

• Bad packets are filtered

A packet switch where the switch starts forwarding that frame (or packet) before the whole frame has been received, normally as soon as the destination address is processed. This technique reduces latency through the switch, but decreases reliabilityReads only part of the packet

The addresses header Packet is forwarded accordingly

Bad packets are not filtered

Cut throughSwtich

Straight andForward Switch

Bus Topology

57

Topic

Network Connectors

Hubs are Layer-1 devices that physically connect network devices together

for communication. Hubs can also be referred to as repeaters.

Hubs provide no intelligent forwarding whatsoever. Hubs are incapable of

processing either Layer-2 or Layer-3 information, and thus cannot make

decisions based on hardware or logical addressing.

Multilayer switching is a generic term, referring to any switch thatforwards traffic at layers higher than Layer-2. Thus, a Layer-3 switch isconsidered a multilayer switch, as it forwards frames at Layer-2 and packetsat Layer-3.A Layer-4 switch provides the same functionality as a Layer-3 switch, butwill additionally examine and cache Transport-layer application flowinformation, such as the TCP or UDP port.

Layer-3 routing is the process of forwarding a packet from one network toanother network, based on the Network-layer header. Routers build routingtables to perform forwarding decisions, which contain the following:• The destination network and subnet mask• The next hop router to get to the destination network• Routing metrics and Administrative Distance

A switch is defined as a device that allows a LAN to be segmented.

-The segments will operate under the same protocol

Improve the network performance and reliability Better manage the network in general.

59

1 OSI Reference Model

2 TCP/IP Model

3 LAN and WAN

4 Network Topologies

5 Network Technologies

Topics list covered in the assignment

Huh, Finally Done!

6 Transmission Medium

7 Communication

8 Network Units

9 Switching Technologies

10 Network Connectors

QUESTIONS

?

THANK YOU!